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Partial characterization of the mitogenic action of pp60 v‐src , the oncogenic protein product of the src gene of avian sarcoma virus
Author(s) -
Durkin Jon P.,
Whitfield James F.
Publication year - 1984
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041200205
Subject(s) - proto oncogene tyrosine protein kinase src , thermolabile , biology , microbiology and biotechnology , growth factor , platelet derived growth factor receptor , kinase , biochemistry , receptor , enzyme
NRK cells infected with a temperature‐sensitive, transformation‐defective mutant of avian sarcoma virus (ASV), ts LA23, are transformed at 36°C, but at 40°C they behave as nontransformed cells because of the inactivation of the abnormally thermolabile pp60 v‐src product of the virus' transforming src gene. At 40°C, these ts LA23‐NRK cells were arrested in G 1 /G 0 by severe serum deprivation. They were induced to enter G 1 , initiate DNA synthesis 7 or 10 hours later, and then divide as (1) nontransformed cells by adding serum or platelet‐derived growth factor (PDGF) at 40°C, or (2) transformed cells by lowering the temperature to a pp60 v‐src ‐activating 36°C without adding exogenous growth factor(s). The level of pp60 v‐src kinase activity rose dramatically in these serum‐deprived cells within 30 minutes of lowering the temperature to the permissive 36°C, and it fell just as rapidly when the cells were returned to the restrictive 40°C. As little as a 2‐hour exposure to 36°C, with an attendant 2‐hour burst of pp60 v‐src kinase activity, was enough to stimulate serum‐deprived ts LA23‐NRK cells to transit G 1 and initiate DNA replication, but not to divide. Much more prolonged pp60 v‐src activity was needed for these serum‐deprived cells to complete their cycle and divide. The prereplicative development of quiescent ts LA23‐NRK cells stimulated by serum or PDGF was accompanied by greatly increased protein synthesis and slightly decreased protein degradation, but the pp60 v‐src ‐stimulated cells progressed through G 1 and initiated DNA replication without appreciably affecting the protein synthetic machinery of the cell. The cells stimulated by the mitogenic action of pp60 v‐src , like the cells stimulated by serum, needed to activate early prereplicative genes in order to initiate DNA replication. The needed RNA transcripts induced by serum and pp60 v‐src were produced with comparable efficiency, although it took longer for pp60 v‐src ‐stimulated cells to translate these transcripts and to initiate DNA replication, probably because of their unstimulated protein‐synthetic machinery.